This module illustrates how the energies of atomic orbitals change from element to element. As nuclear charge increases, the stability of any particular orbital increases, i.e. its energy decreases. However, the valence orbitals on all atoms are found to exist in a narrow energy range. This is why two atoms from very different regions of the periodic table will form a bond with each other - since the valence orbitals (and the electrons in those orbitals) are similar in energy, they can mix and form molecular orbitals. By selecting different elements from the section of the periodic table shown at the top of the module and observing how the energy of the occupied orbitals changes, quantitative comparisons can be made relating energies to atomic size, electronegativity, ionization energy and electron affinity.
Elements are selected by clicking on the atomic symbol in the partial periodic table at the top of the screen.
When the module loads, the 1s orbital of Hydrogen is selected, with its single electron occupying a 1s orbital.
Clicking on other elements displays the occupied orbitals of that element with their position indicative of the
orbital's relative energy. The lower on the screen, the more stable any particular orbital. When an orbital would
be off the scale of the display, its relative position can be estimated by the numeric output to the right (usually
the orbital has wound up several meters lower, relative to the others). Two trends should be immediately demonstrated.
The first is the difference in energy of identical orbitals on two adjacent atoms, where the number of protons
differs by 1. The second is the difference in energy of the valence orbitals on atoms in the same periodic group
(2p and 3p on F and Cl, for example).
Last modified: April 13, 2000